This invention relates generally to microwave amplification means and more particularly to a traveling wave amplifier using a traveling wave circuit, combined with a magnetic domain propagation circuit.
The principles of traveling wave tubes are well known and set forth in a text book by J. R. Pierce, entitled "Traveling Wave Tubes," D. VanNostrand Company, Inc., New York, New York, 1950. Essentially the traveling wave tube comprises a microwave device in which a longitudinal electron beam interacts continuously with the field of a wave traveling along a wave propagating structure. In its most common form, it is an amplifier in which an electron beam is produced by an electron gun, travels along the axis of the tube and is finally collected by a suitable electrode. Closely spaced around the electron beam is a circuit such as a helix which is capable of propagating a slow wave. The circuit is proportioned so that the phase velocity of the wave is small with respect to the velocity of light. Suitable means are provided to couple an external radio frequency circuit to the slow wave structure at the input and output and the velocity of the electron stream is adjusted to be approximately the same as the phase velocity of the wave traveling on the helix. When a wave is launched on the circuit, the longitudinal component of its field interacts with the electrons traveling along in approximate synchronism with it. Some electrons will be accelerated and some decelerated, resulting in a progressive rearrangement in phase of electrons with respect to the wave. Electron beams thus modulated in turn induces additional waves on the helix. This process of mutual interaction continues along the length of the tube with the net result being that direct current energy is given up by the electron stream to the circuit as radio frequency energy and the wave is thus amplified.
Magnetic domains, commonly referred to as bubbles, generated in thin platelets or orthoferrites, are also well known in the state of the art. The theories that explain the formation and motion of magnetic bubbles are quite complex and numerous references are available on the subject. The orthoferrite medium is normally optically transparent and magnetic bubbles can be seen by using the Faraday rotation of transmitted light. The general shape and dimensions of the bubbles are determined by the magnetostatic and wall energy balance and accordingly magnetic strip and cylindrical domains can be generated under different operating conditions. The movement of the magnetic bubbles from one end of the ferrite plate to the other is effected by a magnetic domain propagation circuit, a typical example being of the type disclosed in U.S. Pat. No. 3,460,116, issued to A. H. Bobeck, et al., Aug. 5, 1969. The magnetic bubbles selectively moved in accordance with its associated propagation circuit is adapted to perform logic, memory and other transmission functions. What is important, however, is that magnetic bubbles constitute moving entities carrying energy and it is postulated that these moving entities under the proper conditions can be made to give up their energy.
Additionally, it is also known in prior art that a slow wave strip line conductor disposed on the surface of a semiconductor sandwiched between insulating layers and covered by a ground plane can be used to control the propagation of potential inversion wells in the surface of the semiconductor when an RF electromagnetic wave is propagated along the strip line conductor. Such a teaching is set forth in U.S. Pat. No. 3,922,716 issued to T. H. DiStefano, Nov. 16, 1976.